Currently, it is common practice to supply medical solutions for parenteral (e.g., intravenous) administration in the form of disposable, flexible pouches. Such medical solutions can include, for example, parenteral, enteral, dialysis solutions, nutrients, and pharmacologic agents, including gene therapy and chemotherapy agents. The pouches should meet a number of performance criteria, including collapsibility, optical clarity and transparency, high-temperature heat-resistance, and sufficient mechanical strength to withstand the rigors of the use environment. Medical solution pouches should also provide a sufficient barrier to the passage of oxygen and other gases to prevent contamination of the solution contained therein.
In addition, there are a number of factors that can limit the ability to store at least certain medical solutions. For example, due to stability, compatibility or other concerns, a number of medical solutions cannot be premixed. Rather, the individual components must be stored separately. Typically these components are either stored in separate containers and admixed before use, or are stored in separate compartments of a single flexible container and mixed prior to use. For example, amino acids and dextrose solutions require storage in separate containers or compartments before use.
Typically, prior to administering a medical solution from a pouch and into a patient, a medical professional visually inspects the solution contained within the pouch. Such an inspection provides a cursory determination that the medical solution to be administered is of the proper type and has not deteriorated or become contaminated. In this regard, it is advantageous that the pouch have excellent optical properties, i.e., a high degree of clarity and transmission and a low degree of haze. A medical solution pouch having poor optical properties can render a visual inspection of the packaged solution ineffective, thereby triggering the medical professional to needlessly discard the pouch. Also, the medical professional could fail to notice a solution that is of the wrong type, or that had deteriorated or become contaminated. As will be discussed herein below, the industry-wide practice of heat-sterilizing solution-containing medical pouches greatly exacerbates the problem of maintaining good optical properties in such pouches.
Heat-sterilization of medical pouches typically occurs in an autoclave at about 250° F. for periods of about 15 to 30 minutes. Steam is generally used as the heat-transfer medium. Heat-sterilization is normally performed by the manufacturer and/or packager of the medical solution prior to sending the packaged medical solution to the end user. Heat sterilization is done to help ensure that the medical solution as packaged in the pouch is substantially free from contamination. Thus, another requirement of medical solution pouches is that they must be able to endure the high temperatures encountered during heat-sterilization without deterioration by, e.g., developing a heat-seal leak or other type of containment failure.
Medical solution pouches should also have sufficient mechanical strength to withstand the abuse that is typically encountered in the use environment. For example, in some circumstances, a plastic or rubber bladder is placed around a medical solution-containing pouch and pressurized to force the solution out of the pouch and into a patient. Such a bladder is commonly referred to as a “pressure-cuff” and is used, for example, when a patient is bleeding profusely in order to quickly replace lost fluids. Medical solution pouches should have sufficient durability to remain leak-free during such procedures.
Flexible pouches can be made from an ethylene vinyl alcohol copolymer (EVOH). However, EVOH can exhibit various undesirable properties when used as a medical solution pouch. Typically, when prior art films containing EVOH are subjected to autoclave conditions, the increased temperature, moisture, and pressure results in loss and/or degradation of the EVOH barrier function. Similarly, when prior art films containing EVOH are subjected to rewetting or high relative humidity conditions, as would be experienced during an accidental package leakage, etc., exposure to moisture typically results in loss or degradation of the EVOH barrier function. While the loss or degradation of barrier function in the above situations can be temporary, significant amounts of one or more gases (e.g., oxygen) can nonetheless penetrate the film. In medical, food, and other such applications, such loss or degradation of film barrier functions can result in contamination of the products packaged therein.
It would thus be desirable to provide a pouch comprising EVOH that provides the collapsibility, optical clarity, sterilization, premixing, and strength properties advantageous in medical and related applications.